1. Field of the Invention
This invention relates to an electrophotographic apparatus, and more particularly to a transfer-fixing device in such apparatus.
2. Description of the Prior Art
In order that a developed image on the surface of a photosensitive medium may be transferred onto a transfer medium and fixed thereon, the electrophotographic copying apparatus has heretofore required two process steps, i.e., the step of transferring the developed image from the surface of the photosensitive medium and the step of fixing the transferred image on the transfer medium. The transfer step has been done with the transfer medium brought into contact with the surface of the photosensitive medium by means of a transfer roller or a transfer corona discharger. However, this has lead to various problems in that pieces of the transfer medium or dust tend to stick to and damage the surface of the photosensitive medium; when the surface of the photosensitive medium is cleaned the dust or other foreign materials tend to mix with recovered developer to make such developer unfit for reuse, and invasion of the dust or other foreign materials into the developing device reduces the developing efficiency. The fixing step has been effected either by heating the transfer medium with the developed image thereon by irradiating such transfer medium with an infrared ray lamp or the like during the transport of the transfer medium, or by heating the transfer medium as it is passed on a hot plate. However, these techniques result in a great loss of heat and accordingly a reduced heating effect when heat is applied to the transfer medium for melting-fixing or for dry fixing. Further, according to the prior art, the developed image has been transferred onto the transfer medium and then the transfer medium has been transported to the fixing step, whereas the transfer medium, which is usually flexible, has been subject to vibrations during the course of such transport, which in turn has resulted in disturbance of the transferred image on the transfer medium. All of these problems have been very inconvenient to overcome.